Van der Waals (vdW) clusters of naphthalene with argon were synthesized in supersonic beam expansions. Mass-selective absorption spectroscopy was carried out by using fragmentation-free two-color resonant two-photon ionization with mass-spectrometric detection. Electronic spectra of naph⋅Arn (n≤6) were recorded at the vicinity of the naphthalene S1←S0 electronic origin (32 020 cm−1 ), and corresponding spectra for the 8̄10 transition up to n=30. For n=3, the spectra due to two different isomers could be separated. Clear evidence for the existence of different cluster isomers was also found for n=6, 8, 9, 12–14, and 25–28. In comparison with most other solvent clusters M⋅Arn (M is the aromatic molecule), the spectral red shifts of 000 and vibronic bands of the naph⋅Arn clusters are very small. Analysis of the size dependence of the electronic spectral shifts indicates that the stepwise solvation of the naphthalene molecule proceeds predominantly on one side of the molecule. Two semicyclic trends in the spectral shifts are interpreted as successive wetting-nonwetting transitions which occur with increasing solvent cluster size. In the proposed mechanism for these transitions, part of the innermost solvent layer ‘‘unwets’’ the substrate, and moves to the second or third layer, thereby forming a nonwetting dropletlike cluster on one side of the naphthalene substrate.